Lophophine, also known as 2C-MMDA-1 or as 3-methoxy-4,5-methylenedioxyphenethylamine (MMDPEA or MMDPEA-1), is a putative psychedelic and entactogen drug of the methylenedioxyphenethylamine family. It is the α-demethylated homologue of MMDA, and is also closely related to mescaline (3,4,5-trimethoxyphenethylamine) and MDPEA.

Alexander Shulgin reported in his publications that lophophine is active in the dose range of 150 to 250 mg orally. He states that at these doses, lophophine has some similarity to mescaline in action, in producing a peaceful elevation of mood, euphoria, and mild enhancement of visual perception, but without the generation of closed-eye mental imagery. Shulgin also notes that, in contrast to mescaline, lophophine causes no nausea. He estimated that it was about twice the potency of mescaline.

Alexander Shulgin originally suggested that lophophine may be a natural constituent of peyote (Lophophora williamsii) due to it being the only logical chemical intermediate for the biosynthesis of several tetrahydroisoquinolines known to be present in this cactus species. Subsequently, lophophine was indeed shown to be a minor component of both peyote and San Pedro cactus.